The invention relates to a disc brake, in particular for a commercial vehicle, having a brake caliper that straddles a brake disc and is designed as a sliding caliper, the brake caliper being secured on a fixed brake carrier, a brake application device, by which an associated, application-side brake pad can be pressed against the brake disc during braking, and at least one restoring device having a return element, by which the brake caliper can be brought into an initial position after movement due to braking and release of the brake.
When the brake application device of a sliding caliper disc brake of this kind is actuated, the action-side, i.e. the application-side, brake pad is first of all pressed against the brake disc and, as the operation progresses, the reaction forces which arise press the brake caliper against the other side of the brake disc, taking the opposite, reaction-side brake pad along in the process.
In order to move the brake caliper into an initial position after release of the application force and thus to prevent the brake pads from resting in sliding contact with the brake disc, even if free from braking forces, which leads to the brake running hot and to excessive abrasion of the friction facing of the brake pads, the use of a restoring device is proposed in DE 10 2007 001 213 A1, for example.
In the case of the disc brake known therefrom, a restoring device is provided on the application side in one of the guide bars by means of which the brake caliper is held movably on the brake carrier. The restoring device has an elastically deformable return element, specifically a compression spring, by which the brake caliper is moved automatically into an initial position.
To perform these, so to speak, multifunctional tasks, the guide bar or the sliding bearing formed must be modified accordingly, requiring special production measures. This also takes account of the aspect that one of the two bearings with which the respective guide bar is associated is designed as a floating bearing and the other bearing is designed as a fixed bearing.
DE 22 30 949 A1 discloses a disc brake in which the return element is formed from a leaf spring, by means of which the brake pad is likewise pulled out of the region of contact with the brake disc in the unloaded position.
However, there is a very pronounced change in the characteristic of this leaf spring due to the extent of wear of the brake pad, with the result that uniform retraction of the brake pad or a uniform retraction distance is not guaranteed.
It is the underlying object of the invention to develop a disc brake of the type in question in such a way that it is of simpler structural design and that its service life, in particular that of the brake pads and of the brake disc, is increased.
This and other objects are achieved by a disc brake, in particular for a commercial vehicle, having a brake caliper that straddles a brake disc and is designed as a sliding caliper, the brake caliper being secured on a fixed brake carrier, a brake application device, by which an associated, application-side brake pad can be pressed against the brake disc during braking, and at least one restoring device having a return element, by which the brake caliper can be brought into an initial position after movement due to braking and release of the brake. The restoring device is held both in the brake caliper and in the brake carrier on the opposite side of the brake disc from the brake application device.
By arranging the restoring device on the opposite side from the brake application device, the side facing the reaction-side brake pad, effective, in particular automatic, return of the brake caliper is achieved at the same time as minimum interference with the rigidity of the system.
Thus, support for the restoring device in the brake caliper and in the brake carrier is possible in a region situated outside high bending stresses during braking. If appropriate, a locating lug for supporting the restoring device can be formed integrally during the production of the brake caliper, which is usually composed of cast iron.
Two restoring devices are preferably provided, more specifically outside the region of overlap of the brake pad. The forces which arise are thus absorbed uniformly.
To compensate for a change in the release clearance, i.e. the spacing between the brake pads and the brake disc, due to deformation of functional parts such as the brake caliper, the brake application mechanism or the like, and to abrasion of the brake pads caused by braking, an adjustment device is integrated into the restoring device, ensuring that said changes in the functional parts have no effect on the functional behavior of the disc brake overall.
A preferred variant embodiment of the invention provides a bolt firmly connected to the brake carrier.
A sleeve is positioned in a fixed manner in the brake caliper and is held, in turn, in a hood-type cover pressed into the brake caliper, wherein a return element and the adjustment device are positioned in the sleeve.
The return element consists of a compression spring, especially a spring assembly consisting of diaphragm springs, which is supported, on the one hand, on the sleeve, which thus forms an abutment, and, on the other hand, on a clamping ring, which forms the adjustment device.
The sleeve has two stops arranged with a spacing relative to one another in the direction of movement of the brake caliper, between which the clamping ring is arranged, wherein the thickness of the clamping ring, which surrounds the bolt with a clamping action, is less by the predetermined release clearance than the spacing between the two stops. During a braking operation, in which, as described, the brake caliper is moved, taking the reaction-side brake pad along in the direction of the brake application device, as the reaction forces take effect, the compression spring is simultaneously stressed, i.e. compressed, and the gap defining the release clearance between one stop and the clamping ring is closed.
After release of the brake, the compression spring expands and pushes the sleeve and hence the brake caliper into an initial position, in which the second stop rests against the clamping ring and the gap between the clamping ring and the first stop is reestablished.
Wear adjustment is performed with the aid of the clamping ring, with the compression spring being largely compressed during the reaction-induced movement of the brake caliper. If, owing to wear, the associated brake pad is not yet resting on the brake disc, the brake caliper is moved further, overcoming the friction forces acting on the bolt by virtue of the clamping ring, with a movement of the clamping ring and hence of the brake caliper relative to the bolt in the direction of the brake disc taking place and the spacing between the brake caliper and the brake disc decreasing.
After release of the brake, the brake caliper, which has been moved relative to the bolt by the amount of wear or component deformation, is pushed back into its end position, this travel being determined as before by the spring travel of the compression spring, which corresponds to the desired release clearance.
The holding force of the clamping ring is produced by radial stress, for which purpose the clamping ring, which is otherwise held with a radial undersize in the sleeve, has a through slot. Before assembly, i.e. before the clamping ring is placed on the bolt, the inside diameter of the clamping ring is less than the outside diameter of the bolt. After the clamping ring has been fitted, the internal restoring forces produce the required preloading force, i.e. clamping force.
The sleeve is preferably designed as a deep-drawn part, wherein the stops for limiting the movement of the brake caliper are produced to correspond with the clamping ring by denting the sleeve.
To install the clamping ring, a stop is first of all produced by pressing in the sleeve, after which the clamping ring is inserted and then the second stop is formed, likewise by pressing in the circumferential surface.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.